National Primary Drinking Water Regulations (NPDWR) – PFAS
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WHAT ARE NPDWR?
NPDWR are legally enforceable rules intended to protect public health by limiting the levels of harmful contaminants in drinking water. NPDWR are established by the U.S. EPA under the authority of the Safe Drinking Water Act (SDWA). Limits are expressed as Maximum Contaminant Levels (MCLs) and Maximum Contaminant Level Goals (MCLGs). MCLs are the maximum permissible levels for contaminants in water. MCLGs are non-enforceable health goals set at levels at which there are no known or anticipated adverse human health effects. NPDWR also specify how often water systems need to sample and at what points in the water system.
WHICH PFAS ARE COVERED BY NPDWR?
In April of 2024, the EPA established the first-ever federally enforceable standards for six PFAS in drinking water: PFOA, PFOS, PFHxS, HFPO-DA (GenX), PFNA, and PFBS. This regulation required all community water systems and non-transient, non-community water systems, regardless of the number of customers served, to monitor for six PFAS compounds. Five of these compounds have individual limits: PFOA, PFOS, PFHxS, HFPO-DA, and PFNA. Because PFAS often occur in mixtures, PFHxS, PFNA, HFPO-DA, along with PFBS are also subject to a hazard index that accounts for the presence of two or more of these compounds in a sample.
NPDWR PFAS LIMITS
| Chemical | Maximum Contaminant Level Goal (MCLG) | Maximum Contaminant Level (MCL) |
|---|---|---|
| PFOA | 0 | 4.0 ppt |
| PFOS | 0 | 4.0 ppt |
| PFNA | 10 ppt | 10 ppt |
| PFHxS | 10 ppt | 10 ppt |
| HFPO-DA (GenX chemicals) | 10 ppt | 10 ppt |
| Mixture of two or more: PFNA, PFHxS, HFPO-DA, and PFBS | Hazard Index of 1 | Hazard Index of 1 |
| Maximum Contaminant Level Goal (MCLG): The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals | ||
The Hazard Index is a tool used to evaluate potential health risks from exposure to chemical mixtures.
*ppt = Parts per trillion (also expressed as ng/L)
Source: EPA Fact Sheet, PFAS National Primary Drinking Water Regulation
HOW TO USE THE NPDWR PFAS HAZARD INDEX
In the graphic to the right, the water droplet represents the concentration of each PFAS in the sample. The denominators are called Health-Based Water Concentrations (HBWC) and represent the level at which no health effects are expected for that PFAS. If the total of all the fractions is equal to or greater than one, the water system exceeds the Hazard Index value. To be considered in violation, the running average of all samples taken in the past twelve months must also be equal to or greater than one.
NPDWR PFAS TEST METHODS
Only EPA test methods 533 and 537.1 may be used for PFAS NPDWR compliance. Many Public Water Systems (PWSs) will already be using both methods to sample drinking water as both are required to analyze for the complete set of 29 PFAS included in the Fifth Unregulated Contaminant Monitoring Rule (UCMR 5). Water systems not required to sample for UCMR 5 may choose either method for NPDWR compliance.
NPDWR PFAS MONITORING REQUIREMENTS
Initial monitoring requirements are based on the size of the water system and the source water used. Water is monitored at entry points to the distribution system, and combined water samples are not allowed. The EPA has said that data from UCMR 5 sampling may suffice for all or some of the initial monitoring requirements. Groundwater systems that serve >10,000 consumers will be required to sample for two additional quarters in addition to their UCMR 5 sampling. In addition, some states have monitoring rules that may also satisfy the requirements if the analysis was conducted using EPA Method 533 or 537.1.
Trigger Levels are used to determine if a system may reduce monitoring (triennial sampling) thereafter. The trigger levels are set at half the MCLs. If all initial sampling test results are below trigger levels, then a system may sample triennially. Otherwise, quarterly sampling is required.
NPDWR ENFORCEMENT TIMELINE
Water systems have until April 2027 to comply with the initial sample requirements
and until April 2029 to address levels of PFAS that exceed the MCLs.
STATE RULES STILL APPLY
Several states have already established enforceable drinking water limits. Any limits set by the state will remain in effect until the NPDWR PFAS limits become enforceable in 2029. For example, if a state has a drinking water limit of 10 ppt for PFOA, water systems covered under that regulation are still required to comply until April of 2029 unless the state alters or abolishes that requirement.
States will continue to be free to set their own limits, provided they are no less stringent than the federal limits. That is, a state may set a new drinking water limit that is higher than the national primary drinking water limits until April of 2029. After that, PWSs will be required to comply with the lowest limits, whether they be state or federal. States may also set limits on PFAS not covered by the NPDWR.
A LABORATORY PARTNER YOU CAN COUNT ON
With more than 40 drinking water laboratories across the country, Pace® is your go-to partner in North America for the analysis of drinking water. You can count on us to provide:
- Reliable Data. Pace® uses only EPA-approved methods 533 and 537.1 for the analysis of drinking water for NPDWR compliance. With Pace® you can count on:
- Confidential Results. We will never divulge client information to outside entities without your express permission.
- Immediate Notification. When NPDWR drinking water limits for PFAS are exceeded, we will notify you immediately.
- Self-Service Access. Our secure customer portal allows clients 24/7/365 near-real-time access to their data.